Applications of the fundamental theorem of calculus

What would be some, for lack of better wording, 'real life' applications of the fundamental theorem of calculus?

While having a discussion with a classmate of mine he said that we can use the theorem ''to solve area problems that we will only encounter in proposed "Real Life" problems, which are never based on anything in anyone's real life, except for nerdy Calculus book authors''

I know that's not true, but I am having trouble coming up with any applications.